JP2007067098A - Micro-bump forming method, its device, and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro-bump forming method for manufacturing micro-bumps in a short period of time for excellently coping with cost reduction, and for achieving the narrowing of a pitch between bumps along with the miniaturization of a package size. <P>SOLUTION: A member to be etched composed of a metal component for making a high-vapor pressure halide is installed into a chamber. The member to be etched is etched with a halogen radical obtained by plasmatizing a halogen gas. Thus, it is possible to generate a precursor as a halide of the metal component, and also to generate only the metal component of the precursor on a wafer 13 by properly controlling temperature conditions of the wafer 13 as a substrate. In that case, the temperature of the wafer 13 is gradually increased from a low-temperature range of forming the thin film of the precursor on the wafer 13 to a high-temperature range of forming only the metal component on the wafer 13. Consequently, it is possible to form a large number of the micro-bumps 29 composed of the metal component on the wafer 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming micro bumps, an apparatus therefor, and a semiconductor device, and is particularly useful when applied to mounting of a semiconductor chip.

  Improvement in the degree of integration of semiconductor chips and mounting technology play a major role in reducing the size and weight of electronic devices. Conventionally, for mounting a semiconductor chip, a lead frame is generally connected by wire bonding and soldered to a printed circuit board via the lead frame. Recently, however, there has been a demand for downsizing electronic devices. In response to the increase in size, a flip chip mounting method in which a semiconductor chip is directly mounted on a printed circuit board has been widely used.

  In this flip chip mounting method, as shown in FIG. 7, a large number of projections called bumps 2 are formed on the back surface of the semiconductor chip body 1, and the circuit of the semiconductor chip I and the wiring of the printed circuit board 3 are connected via the bumps 2. And to connect. That is, the bump 2 is formed of, for example, solder, which is a conductive member brought into contact with the circuit of the semiconductor chip I, and is pressed against the printed circuit board 3 while the semiconductor chip I is placed at a predetermined position on the printed circuit board 3. The bump 2 is heated and melted to bring the tip of the bump 2 into contact with the circuit of the printed circuit board 3. In addition to the solder, gold, silver, copper or the like is also used as the material of the bump 2. In particular, the use of copper bumps is expanding as a material that is inexpensive and has the property of a good conductor.

  The bump formation process for forming the bump 2 is one of the most important processes in the final stage of wafer processing. Here, a solder bump plating process will be described as an example of bump formation. As shown in FIG. 8A, a resist pattern 5 a that is an opening of a resist 5 is formed on a silicon wafer 4. The resist pattern 5a is formed by opening the resist 5 on a wiring terminal portion called a pad 6 connected to a circuit in the semiconductor chip I (see FIG. 7). A barrier metal layer 7 (a metal film for preventing the diffusion of bump metal and imparting conductivity) is formed under the resist 5, and this barrier metal layer 7 is formed from the end of the wafer 4. Electroplating is performed by energizing through. Here, since only the resist pattern 5a is in contact with the plating solution, as shown in FIG. 8B, the bump 2 is formed following the resist pattern 5a. After the bumps 2 are formed by plating, the wafer 4 is moved to the next process, and as shown in FIG. 8C, the resist 5 is peeled off and the barrier metal 7 is etched (unnecessary portions other than the bumps 2). The barrier layer is removed by etching.). Thereafter, the bumps 2 are once melted by heating the wafer 4 in a reflow furnace to form spherical bumps 2 and outgas the bump metal as shown in FIG. 8D.

  In addition, the following patent document can be mentioned as a well-known technique in the said technical field.

Japanese Patent Laid-Open No. 07-273439 Japanese Patent Laid-Open No. 08-236240 JP 09-283925 A

  As described above, the method for forming the bump 2 according to the prior art has many steps, resulting in very poor productivity and time. Further, with recent chip shrink of semiconductor chip I and the increase in pitch, the distance between adjacent bumps 2 is also required to be a narrow pitch of 100 μm or less.

  In view of the above prior art, the present invention provides a microbump formation method and apparatus capable of producing in a short time and excellent in response to cost reduction, and also capable of realizing a narrow pitch between bumps accompanying a reduction in package size, and An object is to provide a semiconductor device.

  Each aspect of the present invention that achieves the above object is based on the following knowledge. That is, the present inventors are a metal component that forms a high vapor pressure halide, and a member to be etched made of a metal component desired to be deposited is placed in a chamber, and the halogen radicals obtained by converting the halogen gas into plasma are used as the halogen radicals. A precursor, which is a halide of a metal component, is generated by etching the member to be etched, and only the metal component of the precursor is formed on the wafer by appropriately controlling the temperature condition of the wafer serving as the substrate. A new type of plasma CVD apparatus and film formation method have been developed (see, for example, Japanese Patent Application Laid-Open No. 2003-147534).

In the above-described plasma CVD apparatus of the new type, the metal film is formed on the wafer by controlling the temperature of the wafer to be lower than the temperature of the member to be etched which is a metal source to be formed. For example, the metal of the etched member Cu, when the halogen gas and Cl _2, the the etched member a high temperature (e.g. 300 ° C. to 700 ° C.), and by controlling the wafer at a low temperature (e.g. 200 ° C. approximately), A Cu thin film can be formed on the wafer. This is thought to be due to the following reaction.

(1) Plasma dissociation reaction; Cl ₂ → 2Cl ^*
(2) Etching reaction: Cu + Cl ^* → CuCl (g)
(3) Adsorption reaction on the substrate; CuCl (g) → CuCl (ad)
(4) film-forming ^{reaction; CuCl (ad) + Cl *} → Cu + Cl 2 ↑ ··· (1)
Here, Cl ^* represents a Cl radical, (g) represents a gas state, and (ad) represents an adsorption state.

  An interesting phenomenon was discovered when an experiment was conducted to form a Cu thin film on a wafer under various conditions by forming a member to be etched of the above-described new type plasma CVD apparatus with Cu. That is, the film is formed by the above-mentioned plasma CVD apparatus while changing the temperature of the wafer from a relatively low temperature region before the Cu thin film is formed on the wafer to a relatively high temperature region where the Cu thin film is formed. When the process was performed, a large number of fine copper bumps (micro bumps) were formed on the wafer. The microbumps having a narrow pitch of 1/100 or less compared to the conventional ones were obtained with the interval between adjacent ones being about 1 μm. This suggests that the pitch between the bumps 2 is about 100 μm or less, in particular, about 20 μm, and can be sufficiently applied to the bumps 2 of the next generation semiconductor chip I aiming at further miniaturization. In addition, the formation process can be realized by one process similar to the film formation process only by controlling the temperature of the wafer, and a dramatic streamlining of the process can be realized as compared with the conventional bump forming method shown in FIG.

The bump formation using the above-mentioned new type plasma CVD apparatus is considered to be caused by the following phenomenon as shown in FIG.
1) A CuCl film is formed on the wafer 13 in the low temperature region (see FIG. 1A).
2) As the temperature of the wafer 13 rises, Cu fine particles, that is, seeds of the microbumps 29 are formed on the CuCl film, and these gradually agglomerate and grow (see FIG. 1B).
3) As the temperature of the wafer 13 further rises, the CuCl film is no longer vaporized, and as a result, the fine particles that have grown and grown are formed as micro bumps 29 on the wafer 13 (see FIG. 1C).

  FIG. 2 is a characteristic diagram showing the above phenomenon as a relationship of the wafer temperature T with respect to the time axis. As shown in the figure, there is a region where CuCl is formed in a relatively low temperature portion, and there is a region where Cu is formed in a relatively high temperature region where the low temperature portion partially overlaps the high temperature portion of this region. Further, it is considered that an etching region for etching the generated Cu exists in the high temperature region. Accordingly, the temperature of the wafer 13 is increased at a constant rate from the region where CuCl is formed toward the region where Cu is formed, and the temperature increase is stopped in the region where Cu is formed before reaching the etching region. (This stop point is indicated by a cross in FIG. 2) Micro bumps 29 having a desired particle diameter can be formed. Incidentally, the micro-bump 29 having a small diameter in a short time reaching the region where Cu is formed in a short time becomes the micro-bump 29 having a small diameter, and the micro-bump 29 having a gentle inclination has a large diameter.

The first aspect of the present invention based on such knowledge is as follows:
A metal component that forms a high vapor pressure halide, and a member to be etched made of a metal component desired to be deposited is placed in the chamber, and the member to be etched is etched with halogen radicals obtained by converting the halogen gas into plasma. In the case where a precursor that is a halide of a metal component is generated and only the metal component of the precursor is generated on the wafer by appropriately controlling the temperature condition of the wafer to be a substrate,
A number of micro bumps comprising the metal component by gradually increasing the temperature of the wafer from a low temperature region where the precursor thin film is formed on the wafer to a high temperature region where only the metal component is generated on the wafer. Is formed on the wafer.

  According to this aspect, a desired micro bump can be formed on the wafer in one step similar to the film forming step only by controlling the temperature of the wafer to gradually increase from a predetermined low temperature range to a high temperature range. As a result, the formation of the micro bumps is remarkably facilitated, and a great merit in terms of cost can be enjoyed.

  The interval between the formed micro bumps can be a narrow pitch of about 1 μm. As a result, not only can it contribute to dramatic downsizing of the semiconductor chip, but when the micro bumps are formed of a catalyst metal, the catalyst metal at this time has a large surface area, so that it is good as a catalyst. Functions can be secured.

The second aspect of the present invention is:
In the first aspect,
In the method of forming micro bumps, a plurality of concave portions are provided on the wafer surface, and the positions of the micro bumps are regulated by the concave portions to form the micro bumps at the positions.

  According to this aspect, the positions of the micro bumps can be defined to have a predetermined arrangement.

The third aspect of the present invention is:
In the first aspect,
A number of patterned metal portions are exposed on the wafer surface, the position of the micro bumps is regulated by the metal portions, and the micro bumps in a state of being in contact with the metal portions at the positions are formed. There is a method for forming micro bumps.

  The particles of the metal component formed on the upper surface of the precursor have a property of being attracted to the metal portion and aggregated. Therefore, according to the present embodiment, the positions of the micro bumps are defined to have a predetermined arrangement, and can be connected to, for example, a semiconductor chip or a circuit portion of the substrate via the metal portion.

The fourth aspect of the present invention is:
In the third aspect,
The patterning is performed by forming a micro bump by embedding the metal component in a plurality of recesses provided on the wafer surface.

  According to this aspect, it is possible to easily and quickly pattern the metal portion on the wafer.

According to a fifth aspect of the present invention,
A cylindrical chamber containing the wafer in a vacuum space;
Working gas supply means for supplying a working gas containing halogen into the chamber;
Plasma generating means for converting the working gas supplied into the chamber into plasma;
It is formed of a material containing a metal capable of generating a high vapor pressure halide, and is disposed in the chamber so as to form a precursor composed of the metal and the halogen by etching with a halogen radical obtained by converting the working gas into plasma. A member to be etched, and
A plurality of micro bumps made of the metal component are formed by gradually increasing the temperature of the wafer from a low temperature region where the thin film of the precursor is formed on the wafer to a high temperature region where only the metal component is generated on the wafer. And a temperature control means for controlling a temperature of the wafer so as to be formed on the wafer.

  According to this aspect, the desired micro bumps are formed on the wafer in one step similar to the film forming step only by controlling the temperature of the wafer through the temperature control means so as to gradually increase from the predetermined low temperature range to the high temperature range. Can be formed. As a result, the formation of the micro bumps is remarkably facilitated, and a great merit in terms of cost can be enjoyed.

  The interval between the formed micro bumps can be a narrow pitch of about 1 μm. As a result, not only can it contribute to dramatic downsizing of the semiconductor chip, but when the micro bumps are formed of a catalyst metal, the catalyst metal at this time has a large surface area, so that it is good as a catalyst. Functions can be secured.

The sixth aspect of the present invention is:
5. A semiconductor device comprising a microbump formed by the microbump forming method according to claim 3 or 4 on a printed circuit board or a semiconductor chip bonded by a flip chip mounting method via a microbump. It is in.

According to this aspect, the semiconductor device can be manufactured at a low cost in combination with the effect that the micro bumps can be easily and economically formed. Furthermore, since the interval between the micro bumps at this time is about 1 μm, the semiconductor device can be remarkably reduced in size.

The seventh aspect of the present invention is
A semiconductor device is characterized in that semiconductor chips are connected to each other through micro bumps formed by the micro bump forming method according to claim 3 or claim 4.

  According to this aspect, in the connection between the semiconductor devices, the same effect as in the sixth aspect is obtained. As a result, it is possible to contribute to downsizing of SoC (System on Chip) to SiP (System in Package).

  According to the present invention, a desired micro bump can be formed on the wafer in one step similar to the film forming step only by controlling the temperature of the wafer to gradually increase from a predetermined low temperature range to a high temperature range. The formation is greatly facilitated and a great cost advantage can be obtained. Further, since the interval between the formed micro-bumps can be a narrow pitch of about 1 μm, a drastic downsizing of the semiconductor chip can be realized.

<Embodiment>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the following embodiment is an illustration and this invention is not limited to the said embodiment.

  FIG. 1 is a schematic side view showing a microbump forming apparatus according to an embodiment of the present invention. As shown in the figure, a support base 12 is provided in the vicinity of the bottom of a cylindrical chamber 11 made of, for example, ceramic, and a wafer 13 is placed on the support base 12. The support base 12 is provided with a temperature control means 16 including a heater 14 and a coolant circulation means 15, and is controlled so that the temperature of the wafer 13 is increased from the predetermined low temperature range while gradually increasing via the support base 12. To do.

  The upper surface of the chamber 11 is an opening, and the opening is closed by a ceramic flat plate 17 made of an insulating material. A plasma antenna 18 for converting the gas supplied into the chamber 11 into plasma is provided above the ceiling plate 17, and the plasma antenna 18 is formed in a planar ring shape parallel to the surface of the ceiling plate 17. . A matching unit 19 and a high-frequency power source 20 are connected to the plasma antenna 18, and high-frequency electromagnetic waves are introduced into the chamber 11 through the plasma antenna 18. That is, the plasma generating means is constituted by the plasma antenna 18, the matching unit 19, and the high-frequency power source 20.

  The member to be etched 21 is formed of a metal (copper in this example) capable of forming a high vapor pressure halide, and is disposed in the chamber 1 below the plasma antenna 18. This member to be etched 21 is for forming a precursor of a metal thin film (copper in this example) produced by the apparatus by an etching action by halogen plasma. Here, the halogen plasma is obtained by converting a working gas containing halogen (chlorine in this example) supplied into the chamber 11 into plasma using high-frequency electromagnetic energy supplied by the plasma antenna 18.

  The member to be etched 21 includes a rod-shaped protrusion 22 and a ring 23, and each protrusion 22 is directed toward the center of the chamber 1 without contacting the tip of the adjacent protrusion 22. Each base end portion is fixed to the ring portion 23 so as to extend. Thereby, each protrusion 22 has an electrically independent structure, and is devised so as not to shield the electromagnetic field formed by the plasma antenna 18 and introduced into the chamber 11.

  The action of supplying a working gas 31 containing chlorine as a halogen (a working gas diluted with He to a chlorine concentration of ≦ 50%, preferably about 10%) 31 around the cylindrical portion of the chamber 11 A plurality of nozzles 24 as gas supply means are connected at equal intervals in the circumferential direction (for example, eight locations: two locations are shown in the figure). The working gas 31 is sent to the nozzle 24 via a flow rate controller 25 that controls the flow rate and pressure of the working gas 31.

  Gases that are not involved in the film formation are exhausted from the exhaust port 28, and the interior of the chamber 11 closed by the ceiling plate 17 is maintained at a predetermined vacuum pressure by a vacuum pump (not shown).

  A micro bump forming method using such a micro bump forming apparatus will be described with reference to FIG. As shown in FIG. 4A, concave portions 13 a having a regular positional relationship are formed on the surface of the wafer 13.

In a state where the wafer 13 is placed on the support table 12 in the chamber 11, Cu is embedded in the recess 13 a. That is, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-264158, the member to be etched is controlled by the plasma 33 of Cl ₂ gas as the working gas while controlling the temperature and temperature difference between the member to be etched 21 and the wafer 13 as predetermined. 21 is etched to form CuCl which is a precursor 34 of a Cu component and Cl ₂ gas. Then, the precursor 34 is adsorbed on the wafer 13, and then a Cu component is deposited to form a Cu thin film, and the Cu film formed by this film formation reaction is etched with Cl ₂ gas plasma. In addition to coexisting with the etching reaction to be performed, a Cu film is laminated on the concave portion 13a in order from the bottom by controlling the film formation reaction speed to be higher than the etching reaction speed, and Cu is formed in the concave portion 13a. Embed. As a result, as shown in FIG. 4B, a Cu buried portion 26 is formed. The embedded portion 26 can function as an electrical connection portion, for example, connected to a circuit in a semiconductor chip.

  In this state, the temperature control means 16 gradually increases the temperature of the wafer 13 from a low temperature region where the precursor thin film is formed on the wafer 13 to a high temperature region where only the metal component is generated on the wafer 13. As a result, in the initial low temperature range, as shown in FIG. 4C, a CuCl film 27 is formed on the wafer 13.

  Next, as the temperature of the wafer 13 rises, as shown in FIG. 4D, Cu fine particles, that is, seeds of microbumps 29 are formed on the CuCl film 27, and these gradually agglomerate and grow.

  Further, when the temperature of the wafer 13 rises, the CuCl film 27 is not vaporized. As a result, as shown in FIG. 4 (e), the fine particles that have grown in an agglomerated manner are formed on the wafer 13 as microbumps 29. When agglomerating, Cu fine particles are attracted to Cu in the embedded portion 26, and as a result, the seeds of the microbump 29 grow at a predetermined position corresponding to the embedded portion 26.

  FIG. 5 is a photomicrograph showing the micro bump 29 formed by the micro bump forming apparatus according to the present embodiment. Referring to the figure, it can be seen that a large number of micro bumps 29 are regularly formed on the wafer 13. At this time, the interval between adjacent micro bumps 29 is 1 μm.

<Other embodiments>
In the above embodiment, the patterning of the metal portion on the wafer 13 is performed using the embedding function as the film forming apparatus of the micro bump forming apparatus, but the present invention is not limited to this. Any conventionally known patterning method can be used without limitation.

  In addition, in order to ensure electrical connection, it is necessary to regularly form the micro bumps 29 at predetermined positions. In other applications, the micro bumps 29 are formed at regular positions. You don't have to. In the case where the micro bumps 29 are formed of a catalyst metal and function as a catalyst, a large number of micro bumps 29 may be formed on the wafer 13 at intervals.

<Application example>
According to the microbump forming method of the present invention, a large number of microbumps 29 made of a metal such as Cu can be formed easily and at a narrow pitch, so that the semiconductor chip I (see FIG. 7) is printed on a printed circuit board. 3 (see FIG. 7) can be applied as a bump 2 when flip-chip mounting. In this case, the semiconductor device can be manufactured at a low cost in combination with the effect that the bump 2 can be formed easily and economically. Furthermore, since the distance between the bumps 2 at this time is about 1 μm, the semiconductor device can be remarkably reduced in size. The bump 2 at this time may be formed on the printed circuit board 3 side.

  The micro bump 29 according to the present invention can be applied to the connection between semiconductor devices, and exhibits various excellent effects. For example, as shown in FIG. 6, a SiS (silicon-in-silicon) architecture in which semiconductor chips are connected by micro bumps 29 can be easily formed. In the figure, 50 is a SiIP (silicon interposer), 51 is an ASIC, and 52 is a SiS-DRAM. In addition, the present invention can be applied to a connection portion in SoC (System on Chip) to SiP (System in Package), and can contribute to miniaturization of these elements.

  The present invention is suitable for use in the industrial field for reducing the size of semiconductor devices.

It is explanatory drawing for demonstrating the formation process of the microbump which concerns on this invention. It is a characteristic view which shows the phenomenon shown in FIG. 1 as a relationship of the wafer temperature with respect to a time-axis. It is a schematic side view which shows the microbump formation apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows a mode that a microbump is formed in the apparatus shown in FIG. It is a microscope picture which shows the microbump formed in the apparatus shown in FIG. It is explanatory drawing which shows the SiS (silicon in silicon) architecture which is an example at the time of connecting semiconductor chips with the micro bump which concerns on this invention. It is explanatory drawing which shows the mounting aspect of the semiconductor chip by the flip chip system based on a prior art. It is explanatory drawing for demonstrating each process of the flip chip system which concerns on a prior art.

Explanation of symbols

I Semiconductor chip 2 Bump 11 Chamber 12 Support base 13 Wafer 13a Recess 16 Temperature control means 18 Plasma antenna 21 Etched member 26 Embedded portion 27 CuCl film 29 Micro bump 31 Working gas 33 Plasma 34 Precursor 50 SiIP
51 ASIC
52 SiS-DRAM

Claims (7)

A metal component that forms a high vapor pressure halide, and a member to be etched made of a metal component desired to be deposited is placed in the chamber, and the member to be etched is etched with halogen radicals obtained by converting the halogen gas into plasma. In the case where a precursor that is a halide of a metal component is generated and only the metal component of the precursor is generated on the wafer by appropriately controlling the temperature condition of the wafer to be a substrate,
A number of micro bumps comprising the metal component by gradually increasing the temperature of the wafer from a low temperature region where the precursor thin film is formed on the wafer to a high temperature region where only the metal component is generated on the wafer. Is formed on the wafer. In claim 1,
A method for forming a microbump, wherein a plurality of recesses are provided on the wafer surface, the position of the microbumps is regulated by the recesses, and the microbumps are formed at these positions. In claim 1,
A number of patterned metal portions are exposed on the wafer surface, the position of the micro bumps is regulated by the metal portions, and the micro bumps in a state of being in contact with the metal portions at the positions are formed. Micro bump formation method. In claim 3,
The patterning is performed by embedding and depositing the metal component in a plurality of recesses provided on the wafer surface. A cylindrical chamber containing the wafer in a vacuum space;
Working gas supply means for supplying a working gas containing halogen into the chamber;
Plasma generating means for converting the working gas supplied into the chamber into plasma;
It is formed of a material containing a metal capable of generating a high vapor pressure halide, and is disposed in the chamber so as to form a precursor composed of the metal and the halogen by etching with a halogen radical obtained by converting the working gas into plasma. A member to be etched, and
A plurality of micro bumps made of the metal component are formed by gradually increasing the temperature of the wafer from a low temperature region where the thin film of the precursor is formed on the wafer to a high temperature region where only the metal component is generated on the wafer. And a temperature control means for controlling the temperature of the wafer so as to be formed on the wafer.   5. A semiconductor device comprising a microbump formed by the microbump forming method according to claim 3 or 4 on a printed circuit board or a semiconductor chip bonded by a flip chip mounting method via a microbump. . A semiconductor device, wherein semiconductor chips are connected to each other through micro bumps formed by the micro bump forming method according to claim 3.

Images